What do I need to start making Let's Plays & walkthroughs of video games on YouTube?

Usually programs like fraps can record both your voice and the gameplay. Or ou can first record the gameplay, then do a separate audio file on your commentary. You need to buy fraps and a decent microphone. I got a good one at Microcenter for about 20 dollars, but some are cheaper lol. Once you have those, just look up tutorials on Google on how to commentate games or something. Google is your friend :)